Brian,
Since we first released the original Mode C 'Beta', Lee has done a considerable amount of work to reduce spurious alerts, as a result of which these are now much less prevalent than with the original Mode C software. Work on this issue is however still ongoing to try to improve things even further, so track files indicating spurious alerts will all be useful.
The best method of transfer for large files is to put them in 'Dropbox' (you can set up a limited size Dropbox account for free). Put the files you want to allow access to in a folder and PM a link to that specific folder to 'Admin' (or anyone else) via the 'Messages' Board. (Right click on the folder and you will see an option to 'Copy Dropbox Link'). If your Dropbox gets too full, you can just delete files or move them over to store elsewhere on your PC or wherever.
Regards
Peter
(PilotAware Engineering)